1. Field of the Invention
The present invention relates to a method of and an apparatus for producing hooks on surface-type fasteners known as hook-and-loop fasteners by cutting uncut loops on a base sheet on one of the legs thereof.
2. Prior Art
According to a known method and apparatus disclosed in Japanese Patent Publication No. 42-13511, published Aug. 1, 1967, and reillustrated here in FIGS. 7 and 8, a comb-line stationary cutter blade A of a given thickness and a pair of comb-like movable cutter blades B, B disposed on opposite sides of the stationary cutter blade A are inserted into loops C on a base sheet while the latter is fed along a path, and then the movable cutter blades B, B are horizontally reciprocated to cut the loops C on one of the legs thereof simultaneously at two different points, thereby producing hooks each of which has a relatively large loop-accepting passage or space substantially equal to the thickness of the stationary cutter blade A.
The known practice, however, has various drawbacks: The cutter blades A, B must be narrow and thin enough to pass through such small loops having a height of about 2 mm and hence they are difficult to manufacture at a low cost. The movable cutter blades B further need to be rigid enough to cut the loops of monofilament. Such rigid but thin movable cutter blades B are likely to be damaged and sometimes broken during the cutting operation. The possibility of cutter breakage increases at the cutting speed or the reciprocating motion of the movable cutter blades B is increased. Additionally, the thin stationary cutter blade A is liable to vibrate in resonance with the reciprocation of the movable cutter blades B, thus making it difficult to cut all the loops at the same points of severance. Consequently, the resulting hooks have non-uniform shapes and configurations and provide only a low strength of engagement when coupled with loops of a mating fastener part. A further disadvantage is that the loop-accepting spaces of the hooks, which depend on the thickness of the stationary cutter blade A, can be adjusted only by replacing stationary cutter blade A with another stationary cutter blade having a different thickness.